1. Field of the Invention
The invention relates in general to an apparatus and a method for signal detection, and more particularly to an apparatus for signal detection with phase rotation and filtering functionality to enhance performance of a receiver and a method therefor.
2. Description of the Related Art
In a typical wireless communication system, a receiver performs demodulation on a received signal to acquire data contained in the received signal. The receiver typically is required for performing an initial synchronization operation to synchronize the receiver with a transmitter with respect to the received signal. For example, in a communications system using time division multiple access (TDMA) technology, such as a global system for mobile communications (GSM) system, the received signal is time-division-multiplexed. After the synchronization operation is completed, the receiver enters a normal mode where the receiver can perform demodulation to extract data contained in the received signal.
Before synchronization and demodulation, the received signal is initially processed and down-converted to a baseband signal with respect to a specific channel. In addition, the baseband signal is further converted to an in-phase component I and a quadrature component Q (I/Q components) of the baseband signal for further processing. The I/Q components of the baseband signal, which includes a tone of a known frequency, e.g. a pilot tone of 67.7 kHz in GSM system, is further down-converted to a tone for the receiver to lock onto in order to perform the synchronization.
A wireless communication device, e.g. a mobile station, detects the single tone by applying a digital signal processor equipped in the mobile phone to directly process the I/Q components of the baseband signal with respect to a selected channel. This approach is straightforward to achieve the synchronization operation with a hardware component. However, the digital signal processor needs to perform complicated computation in order to detect the single tone while possibly requested for services by many other components of the mobile phone to perform other operations. Accordingly, the loading and power consumption of the digital signal processor would be increased, degrading performance of the mobile station. Thus, it is desirable to have an approach to signal detection, especially for single tone detection, to resolve this problem and enhance the performance.